Biotin-Lys-His Blocks Aggregation of RNA-binding Protein TLS, a Cause of Amyotrophic Lateral Sclerosis

Naomi Ueda

doi:10.11648/j.bs.20170304.11

Abstract

RNA-binding protein TLS/FUS is a causative gene for amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). TLS mutations induce the propensity of TLS to form aggregates in motor neurons causing neuronal degenerative lesions to their necrosis. TLS is prone to be precipitated in high concentration around 10 mg/ml, while mutated TLS is suspected to be precipitated even lower or physiological concentration in the motor neurons. An unidentified agent from infections would cause formation of the precipitation of TLS through their surface antigens. The precipitation driven with agents might be attribute to a small compound appeared on the surface. Biotinylated isoxazole (BISOX) has been reported to be precipitated with divergent RNA-binding proteins including TLS in nuclear extracts of cultured mammalian cells. We have published a molecular model for crystal formation of BISOX with TLS providing a plat form for searching novel regulators to precipitate TLS in neuronal disorders. Because BISOX is an artificial compound, we have further explored to obtain naturally occurring agents to induce the TLS precipitation and generated a conceivable biological compound, biotin-Lys-His (BLH). We have examined the precipitation of BLH with HeLa cell nuclear extract, but did not detect any TLS signal. Then, we add BLH to reaction of BISOX with TLS, and serendipitously observed a robust inhibitory effect of BLH on the formation of crystal of BISOX with TLS. We employed in silico analysis to show how BLH blocks the crystal formation of BISOX with TLS. The computational analysis of the events presented a model that BLH should be incorporated into the crystal formation of BISOX but some steric hindrance placed by BLH blocks growing of the crystal of BISOX and TLS. These results provide the potentiality that BLH should block the aggregate formation of TLS in ALS, leading to a seed for drug discovery against ALS, although it needs future endeavor to find more compounds to have effect on the TLS aggregation.

Highlights

RNA-binding protein TLS/ FUS is a causative gene for amyotrophic lateral sclerosis (ALS) [1, 2] and frontotemporal lobar degeneration (FTLD) [3]
We demonstrated that BLH blocks the Biotinylated isoxazole (BISOX) precipitation with TLS
We produced a three-dimensional model to examine interaction among TLS, BLH, and BISOX and obtained the data showing that BLH is incorporated into growing crystal of BISOX with TLS and blocks further formation of the crystal. This prediction suggests that unidentified chemicals suppress the precipitation of RNA-binding protein that is involved in the neurodegenerative diseases

Summary

Introduction

RNA-binding protein TLS (translocated in liposarcoma)/ FUS (fused in sarcoma) is a causative gene for amyotrophic lateral sclerosis (ALS) [1, 2] and frontotemporal lobar degeneration (FTLD) [3]. More than 90% of ALS is sporadic disease in which no genetic background is identified [4, 5]. Around 10% of ALS is familial disease. The causative genes of familial ALS reported are the superoxide dismutase-1 [6], TDP-43 [7], and TLS [1, 2]. Mutated forms of TLS genes indicate the similar pathology with other ALS causative genes, dislocation into cytoplasm from nucleus and the anomalous cytoplasmic inclusions. Mutations in TLS might cause these RNA metabolic functions, suggesting its function as a mediator for biologically active RNA molecules

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Conclusion